On 06/07/2011 03:02 PM, Richard Guenther wrote:
On Tue, Jun 7, 2011 at 2:58 PM, Herman, Geza wrote:
On 06/07/2011 12:27 PM, Richard Guenther wrote:
On Tue, Jun 7, 2011 at 5:51 AM, Herman, Gezawrote:
Hi,
Sorry, if it has been discussed before, I found a lot of information on
strict
On 06/07/2011 12:27 PM, Richard Guenther wrote:
On Tue, Jun 7, 2011 at 5:51 AM, Herman, Geza wrote:
Hi,
Sorry, if it has been discussed before, I found a lot of information on
strict aliasing in gcc, but nothing about this particular case. I'd like to
code a custom container class: it
Hi,
Sorry, if it has been discussed before, I found a lot of information on
strict aliasing in gcc, but nothing about this particular case. I'd
like to code a custom container class: it has a char[] (or dynamically
allocated "char *") for storage, putting an element is done with
placement ne
> I'll try to make a simple example on which GCC produces bad code.
You can find an example below. GCC-4.1 generates bad code (GCC-4.2 is
fine). Neither version give a type-punning warning, though. I'm sorry
that I didn't check gcc-4.2 before I started this thread.
Geza
Here's the code, I c
On Tue, 26 Jun 2007, Andrew Pinski wrote:
> On 6/26/07, Herman Geza <[EMAIL PROTECTED]> wrote:
> > Having the same layout makes them "the same".
> Not in C or C++ and in most cases of fortran too (unless you add an
> attribute).
Yes, it's clear now, thanks
On Tue, 26 Jun 2007 [EMAIL PROTECTED] wrote:
> On Tue, Jun 26, 2007 at 11:42:27PM +0200, Herman Geza wrote:
> > struct Point {
> > float x, y, z;
> > };
> > struct Vector {
> > float x, y, z;
> >
> > Point &asPoint(
On Tue, 26 Jun 2007, Silvius Rus wrote:
> Herman Geza wrote:
> > aliasing when GCC (I think) incorrectly treats types different, but they're
> > the same. For example, I have:
> >
> > struct Point {
> > float x, y, z;
> > };
&g
On Tue, 26 Jun 2007, Silvius Rus wrote:
> Herman Geza wrote:
> > void foo(float *a) {
> > int *b = (int*)a; // type-punning warning
> >
> > // here, access to a and b shouldn't be optimized, as the compiler
> > knows that a and b point to t
On Tue, 26 Jun 2007, Andrew Pinski wrote:
> On 6/26/07, Herman Geza <[EMAIL PROTECTED]> wrote:
> > Maybe GCC shouldn't optimize around invalid type-punnings?
>
> That is what -fno-strict-aliasing is for.
> Also GCC has done this since 3.0.0 (and also 2.95 and 2.95.
Thanks for the answers!
> > Why? Won't the following work?
> >
> > void setNaN(float &v) {
> > union { float f; int i; } t;
> > t.i = 0x7f81;
> > v = t.f;
> > }
> >
> As far as I know, this is guaranteed to work with GCC. But it is not kosher
> according to language standards, so ot
Hi,
gcc's docs states that at -fstrict-aliasing:
"In particular, an object of one type is assumed never to reside at the
same address as an object of a different type, unless the types are almost
the same."
I have problems with this:
struct A {
float x, y;
};
struct B {
float
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